The detection of individuals who are vulnerable for developing schizophrenia requires the identification of markers which are found even in individuals who have not yet developed an episode of disorder. No pathognomonic measure has been identified for risk to schizophrenia, but risk is higher among first degree relatives of schizophrenics. Furthermore, some of the neurophysiological and behavioral indicators which are deviant in schizophrenics also appear deviant in their relatives at greater than normal rates. The purpose of this proposal is to examine a battery of psychophysiological and behavioral measures in brothers of schizophrenics. During the first four years, 150 brothers of male schizophrenic probands will be tested. During the final year, 50 brothers of female schizophrenic probands will be tested. The objective is to verify not only single variables, but also to determine combinations of indicators which may characterize relatives of schizophrenics either with greater sensitivity or specificity. Psychophysiological (smooth pursuit eye movement, event-related potential, pupillographic, cardiac) and behavioral (continuous performance test, span of apprehension, dichotic listening) measures which have been associated with deviant information processing capacities in schizophrenia have been selected. In addition, all subjects (including those recruited as "controls") will be classified according to psychopathological status. It will be possible to examine whether the indicators are associated primarily with schizophrenia-related disorders, or with the occurrence of psychopathology in general, or are independent of clinical status. Thus, we may be able to clarify the utility of either single indicators or patterns of indicators as predictors of vulnerability to the development of schizophrenia.